Taking the domains deletion rate limit as an example, you are allowed to delete up to 60 domains every 60 seconds (1 minute). Should you hit the rate limit, you will need to wait another minute before deleting another domain.

For the username update rate limit, you are able to change your username up to 6 times every 604800 seconds (1 week). Should you hit the rate limit, you will need to wait another week before changing your username again.